Noncorrodible thermostatic elements



1 NONcoBRQDlBLE rmismoSTAT1c ELEMENTS Filed Nov. 14,V 1934 Brassl 35% Zn Patented Octal-2, 1937 `NoNcoiutonlinr: TnERMosL'rA'rIc f Y HELEMENTs Ralph F. Gibbs, Norton, Mass., assignonby mesne assignments, to Laminated Metals Corporation,

a corporation of Rhode Island Application November 14,1934, serial No. '152,991

l 3 claims. (ci. 291-15) My present invention relates to thermostatic elements, and has particular referenceto elements which are non-corrodible and have long life when operating in corrosion-promoting ate mosphere.

The standard `types of thermostatic elements require periodic replacement when used in flue gas passageways, steam radiators, and other installations where corrosion-promoting fluids contact lthe thermostatic metal. To counteract this corrodible effect the thermostatic metal has been surface treated or plated with a resistant material such as vanadium or chromium, but this arrangement has not been satisfactory, as surface currents are induced which produce pitting and eating away of the metal; moreover, the coating slows up the action `of the thermostatic element when subjected to temperature change. `It is the principal object of my invention to provide a thermostatic element composed of non-corrodible metals, thus eliminating need for surface or other protection;

To this end, I have combined non-corrodible steel with brass to obtain a thermostatic element. Although steel and brass have been combined heretofore, the steels possessing `non-corrodible properties, such as chrome steels, have not hitherto been combined with brass because the degree of heat necessary to produce the Joining has been higher than the melting point of the brass. It is a further object of my invention to use a method of joining that does not require4 a temperature sufficiently high to prevent the necessary unit- With the above and other objects and advan-` tageous features in view, my invention consists of a novel thermostatic material and a novel method of producing the same, more fully disclosed in the detailed description followingin conjunction with the accompanying drawing, and more specifically deiined in the claims appended thereto.

The drawing shows a perspective view of a preferr-ed thermostatic metal. j

The non-corrodible steels available for thermostatic useinclude steels having a high chromium content.' A typical steel of this type lis stainless steel, which has a composition of low carbon, low silicon, low copper and high chromium, the chromium ranging from 10 to 25%, and prac-` tically no coefficient of expansion, and may be directly Joined to alow brass by means of hard silver solder, or may be joined to a by the method described hereinafter.

l steel, preferably by high brass A typical composition for stainless steel is as follows: f

Carbon .12 Chromium 16 Silicon h 1 Copper 1 Iron--- 81.88

Sincehigh, brass cannot be welded to steel, and particularly chromium steel, except at a tem- 1 perature sufficient to melt the high brass, I have found it necessary to first join a 10W brass to the means of hard silver solder, and then to join the high brass to the low brass, also preferably by means of hard silver solder. This procedure permits use of. low temperatures which do notcause melting of the brass, whereby a thermal responsive device is obtained having three metals soldered together. A suitable compcsition for the low brass 4is as follows:

Copper 88 zinc h 1o 2 and a suitable composition for the high brass is as follows:

"Copper h W Zinc 35 the low brass havinga coemcient oi' expansion of .0000191 per degree C. and the high brass having a coeiiicient of expansion of .0000202 per degree C.

In manufacturing the thermostatic elements, bars of the different materials, `after being joined by the solder as described, are rolled down to the desired thickness and are then cut in any desired form. In the arrangement using non-'corrodible `steel and low brass, it is preferred to use bars of the same thickness; when both high and low brass are used, the thickness of the low brass bar may be 10%, and of the high brass at least 40% of the total width; and in the arrangement of the two steels and the intermediate brass, it is preferredthat the width of each of the steels be 45% and of the brass 10%.

`It is thus clear that I have joined non-corrosive metals, and particularly high chromium steels and' brass, to produce a. non-corrodible thermostatic element, and that'I have devised a method of uniting these metals which does not require a high temperature for eiecting the joining.

While I have described specific compositions of metals which I have found suitable for the desired Purpose, changes in the materials used. in the compositions and amounts thereof, and in the 'manner of uniting, maybe made to meet particular requirements for thermostatic metals, within the'spirit and the scope of the invention as dened in the appended laims.

I claim:

1. The method of uniting a high brass strip to a high'chromium steel'strip, comprising'iirstjoining a low brass stripl to the steel at a temperature above the melting point of the high brass strip, and then Joining the high brass strip to the low brass strip at a temperature below the temperature required for joining the steel and the low brass strip.

ing substantially 10% of zinc and joined to said m steel strip and said iirst brass strip.

' RALPH F. Grans. 

